Road Runner Nest

Hey all,
I've got a '71 RR non ac car. It has the StratoVent option. The problem I'm having is with the heater/defrost door. It doesn't seem to be opening. I know the cable from the switch on the control panel is connected because the door to the dash vents open when I move the switch to "vent". When I put the switch to heat or defrost, nothing seems to happen. Is the heater/defrost door controled by a vacuum like the vent door? Anyway, what must I do to check and/or fix this .
Thanks.

what happens is the ecu is all vacuum operated no surprise there
rubber and plastic cure overtime and dry rot.
sadly to say there is no stop to this even oem prior to abs plastics
yellow become brittle crack and are of no use for vaccum you can try to replace the switch with oem is you wish however last ones made where in 1974 that you need making it 30+ years that is some aged plastic
there are 3 lever vaccum pod actuators one drivers side two passenger side one controls defroster one controls vent and one controls floor heat
i have replace my unit will all new switches from www.surplussales.com

J Giannini...What swithes are you talking about? Does this surplus store have them? Do you have a pix or P/N?
Thanks

If I could just get them opened, I think I would be satisfied with that.